Even though this book is mainly about Jin, the book actually starts with the story of the Monkey King. The book then switches to Jin's story in the second chapter and, for the third chapter, switches to the story of Danny (Jin's alter-ego). Only after Jin's and Danny's stories do we return to the Monkey King, only to start the same pattern all over again, and repeat it two more times.
For the sake of your sanity (and ours), we'll just give you the general gist of each story, one at a time. If you want every twist and turn of the book, go to the "Detailed Chapter-by-Chapter Plot Summary" and have at it.
Okay, so back to the Monkey King. When we first meet him, he's already been the ruler of his kingdom for a long time. He knows his kung-fu and has mastered all the prereqs he needs to become immortal. But the Monkey King wants more. He wants to become a god and hang out with all the other gods and goddesses, only they don't want him because he is, after all, a monkey. So at a party that he's crashed he starts a fight with one of the gods.
This leads to his banishment from the heavens and to some serious vigilante justice on his part: he goes around beating up all these gods, goddesses, demons and spirits in order to convince them that he's more than just a monkey.
Then he comes across Tze-Yo-Tzuh. Or actually, Tze-Yo-Tzuh seeks him out because everyone's gone and complained to Tze-Yo-Tzuh about the Monkey King. Who is Tze-Yo-Tzuh? Only the creator of all beings and things on Earth, including, of course, the Monkey King.
So Tze-Yo-Tzuh checks the Monkey King. He tries to convince the Monkey King to stop his rampage and just be who he's supposed to be—a monkey—but the Monkey King's not down with that and tries to show how powerful he is. Tze-Yo-Tzuh, unimpressed, buries the Monkey King under a pile of rocks, where the Monkey Kings stays for five hundred years.
Cut to this monk called Wong Lai-Tsao. He's this simple dude: nothing special, just a really nice guy who's into serving others. He's also a faithful follower of Tze-Yo-Tzuh. Tze-Yo-Tzuh chooses Wong Lai-Tsao for a mission, the first step of which is to collect three disciples for his journey. His first disciple is—you guessed it—the Monkey King, who's still trapped under those rocks.
So Wong Lai-Tsao goes to the Monkey King and asks him to free himself from the rocks (Wong Lai-Tsao can't do it since he's just a skinny monk with weak arms) so that he can serve as Wong Lai-Tsao's disciple on the mission. The Monkey King's not having it because he's supposed to be a great sage/deity/ruler: whoever heard of a deity becoming a disciple? But since Wong Lai-Tsao is the Monkey King's last chance at freedom, eventually the Monkey King comes around, breaks free of the rocks, and saves Wong Lai-Tsao from some demons who've been harassing Wong Lai-Tsao during their meeting.
From then on, the Monkey King serves as Wong Lai-Tsao's disciple until the end.
Jin starts out his story by telling us how he got to the town he lives in. The gist? His parents, both immigrants, journeyed to America for a better life (his dad became an engineer; his mom, a librarian) and, once they had Jin, decided to move from place to place until they could find him a place where he could become all that he can be. In other words, they moved to a place with a good school system—a.k.a the suburbs.
Jin's life up until this point was pretty fun, and full of Chinese American kids just like him (they lived in San Francisco Chinatown at first), but in his new town he can't find anyone like him. Kids are mean, and they bully him and call him names. There is this other Asian student, a Japanese American named Suzy Nakamura, but they stay away from each other because the other kids tease them for being part of an arranged marriage.
Anyway, things get a little better once a new Taiwanese kid arrives in town. His name's Wei-Chen Sun, and he looks like a total FOB ("fresh off the boat"). You wouldn't think Jin would want to be friends with Wei-Chen, and he doesn't, but they become friends anyway because Wei-Chen's a really nice guy who has cool toys, like a robot that can change into a robot monkey (think: Taiwanese Transformer).
This is all part of his elementary school years, and by the middle of the book things speed up to Jin's life at a new, mostly white, junior high school. Like a lot of boys, Jin has a thing for that unattainable girl—in his case, it's Amelia Harris, a popular, white girl whom he's liked since 7th grade.
He tells Wei-Chen about his crush and Wei-Chen finagles things so that—eventually—he helps get Jin and Amelia together. They go out on a date after Wei-Chen covers for Jin (something Wei-Chen's not comfortable doing because he has to lie to Jin's parents). The date goes well and Jin's on cloud nine until this popular white guy with curly blonde hair more or less tells Jin to leave Amelia alone. Which Jin does, much to his own shame.
So Jin does something that's way off base: he tries to kiss Suzy Nakamura. What's the big deal? Suzy happens to be Wei-Chen's girlfriend. As expected, Wei-Chen fights with Jin and stops being friends with him.
Totally bummed out, Jin dreams of this old lady herbalist from his Chinatown days. She asks him who he would like to become and—dun dun dun—he wakes up, looks in the mirror, and sees that he's now blonde and white. He gives himself a new name: Danny.
Okay—this is the weird story, but it's super-important because it ties all three stories together at the end.
When we first encounter Danny, he's this blonde, white teenager at the same high school as Jin. (We don't know yet that he's actually Jin.) His life is looking up. He's got this thing going with this blonde girl (who looks a lot like Amelia but isn't), and the jocks are starting to pay attention to him in a good way. It looks like he's someone who's just about to fit in with the popular crowd at school.
But he also happens to have a cousin named Chin-Kee, who's Chinese. And not just Chinese—he's an amped-up version of Fu Manchu with a queue. Chin-Kee is embarrassing. He's loud and spouts a bunch of crazy stuff that turns him into every imaginable, ridiculous stereotype of a Chinese guy; he also goes with Danny to school when he's visiting Danny's family.
Chin-Kee basically ruins Danny's life (in Danny's eyes). He shouts all the right answers in class, he comes on to Danny's girlfriend, he pees in one of the jock's can of Coke—a jock who tries to befriend Danny. Chin-Kee more or less makes Danny's social life at Oliphant High hellish.
Frustrated and angry, Danny fights with Chin-Kee, only to find out that Chin-Kee is like a master of kung-fu. In fact, Chin-Kee is more than a master of kung-fu: he's the Monkey King. Yep—that's what happens to the Monkey King. We find out that he comes annually to visit Danny/Jin as Chin-Kee, but not to keep tabs on Chin-Kee—nope, he's keeping tabs on Wei-Chen, who's actually his son, sent to Earth as a "test of virtue"—to live with humans and still be free of vice.
This doesn't happen, though, and Wei-Chen totally rebels against his father and rejects the teachings of Tze-Yo-Tzuh. So the Monkey King, once he's been revealed to Danny, asks Danny to return to his true form—Jin—in order to go and bring Wei-Chen back from the deep end. (By this time, Wei-Chen's transformed into a Chinese gangsta.)
Jin does just that: He waits for Wei-Chen at a boba tea shop everyday for a month until he sees Wei-Chen one day and convinces him to sit down and talk things out. They do and their bromance returns.